Older wombs linked to complications in pregnant mice

The risks of complications during pregnancy all increase with age. A woman in her late 30s is twice as likely as a younger woman to have a stillbirth, she is also 20% more prone to giving birth prematurely and more likely to experience conditions such as pre-eclampsia. Many of these effects have been linked to the deteriorating quality of ageing egg cells. Yet, this new research, published in Nature Communications, reveals that older wombs also have more trouble adapting to pregnancy.

By examining first pregnancies in aged mice, the team showed that, for mice as for humans, the risk of complications increases with age. Closer examination revealed that the wombs of older mothers are less able to support the growth of a placenta, meaning the developing young have poor blood supply, which slows their growth and can cause birth defects.

The senior author said: "We wanted to enhance our understanding of the increased risks of pregnancy in older mothers. When we compared mice who have their first litter in middle age to their younger counterparts, we found that the lining of the uterus does not respond as well to pregnancy hormones and this delays placenta formation. By identifying the key pathways affected by age in mice we have a better idea of what to look for in humans."

The shorter lifespan of mice means that they are useful for studying the effects of age on pregnancy but these results cannot always be directly applied to human pregnancies. These new results will help to guide long-term studies in humans but it is not yet clear what the implications of these findings will mean for family planning and human healthcare. It is clear that other factors besides egg quality may need to be considered when planning a family.